All Bray PTFE seats and encapsulated discs are molded from pure, virgin PTFE material to the following specifications: thickness 3 mm, specific gravity 2.16, crystallinity 68%. PTFE’s inherent molecular bonding strength gives an excellent chemical, high temperature and tear resistance. Sintered processed PTFE offers lower permeability than melt processed materials such as PFA. These properties combined with Bray’s stringent material specifications provide optimum protection against permeation of the line media.